The goals of this research proposal are to analyze the synthesis, metabolism and regulation of the histone gene products during early embryonic development. We intend to quantitatively measure the rate of transcription, processing and turnover of each of five histone messenger RNAs synthesized during sea urchin embryogenesis and to search for the nuclear precursors to cytoplasmic histone-mRNA. The basic methodological approach is the use of DNA.RNA hybridization techniques. The availability of translated DNA and spacer DNA sequences located adjacent to the protein coding sequences allows a direct analysis of spacer transcription. Thus, we are in a position to follow the fate of both translated and non-translated segments of a putative polycistronic nuclear mRNA precursor. Since the products of these particular genes are so intimately involved in chromosome structure and they are coordinately regulated with DNA replication and the proliferative cycle of the cell, our conclusions will have bearing on understanding of the basic nature of tissue growth, embryonic development and cell differentiation.